» Indian origin scientist says geoengineering could slow down global water cycle

Indian origin scientist says geoengineering could slow down global water cycle

Published: Wednesday, May 28, 2008, 16:18 [IST]

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Washington, May 28 : A new study from a scientist of Indian origin has determined that intentional manipulation of solar radiation by "geoengineering" could lead to a less intense global water cycle.

According to Govindasamy Bala, an atmospheric scientist from Lawrence Livermore National Laboratory, reduction in sunlight and decreasing surface temperatures through "geoengineering" also could mean less rainfall.

In the new climate modeling study, Bala and his colleagues Karl Taylor and Philip Duffy demonstrate that the sunshade geoengineering scheme could slow down the global water cycle.

The sunshade schemes include placing reflectors in space, injecting sulfate or other reflective particles into the stratosphere, or enhancing the reflectivity of clouds by injecting cloud condensation nuclei in the troposphere.

When CO2 is doubled as predicted in the future, a 2 percent reduction in sunlight is sufficient to counter the surface warming.

This new research investigated the sensitivity of the global mean precipitation to greenhouse and solar forcings separately to help understand the global water cycle in a geoengineered world.

While the surface temperature response is the same for CO2 and solar forcings, the rainfall response can be very different.

"We found that while climate sensitivity can be the same for different forcing mechanisms, the hydrological sensitivity is very different," said Bala. The global mean rainfall increased approximately 4 percent for a doubling of CO2 and decreases by 6 percent for a reduction in sunlight in Bala's modeling study.

"Because the global water cycle is more sensitive to changes in solar radiation than to increases in CO2, geoengineering could lead to a decline in the intensity of the global water cycle," said Bala.

But, according to Bala, sunshade geoengineering would not limit the amount of CO2 emissions.

"While geoengineering schemes would mitigate the surface warming, we still have to face the consequences of CO2 emissions on marine life, agriculture and the water cycle," he said.